The majority of stains can be covered to avoid bleeding. Apply a sealer coat of thinned shellac, sanding sealer, or other suitable best outdoor wood sealer after smoothing the painted wood. Shellac can not be used for NGR or water-based stains. If you want to seal the item with polyurethane, double-check that the sealer is compatible. Allow the sealed wood to dry entirely before gently sanding the surface with fine-grit sandpaper. With a tack cloth, remove the sanding debris. As with proper sanding, proper sealing will make all the difference in the outcome of your furniture refinishing project.
Selecting a Sealer
Thinned white shellac is the standard sealer for shellac, lacquer, and natural varnish finishes. This straightforward sealer is composed of one part white shellac (4-pound cut) and three to four parts denatured alcohol. Although shellac is ideal for the majority of refinishing tasks, it cannot be used for polyurethane varnish, water, or non-grain-raising stains.
Where shellac cannot be used, an industrial sanding sealer is the simplest sealer to use. Sanding sealer dries easily and offers an excellent sanding foundation for varnish, shellac, or lacquer. If you want to finish the piece with polyurethane varnish, carefully read the label; certain sanding sealers are incompatible with polyurethane. Sealing is not needed prior to applying a penetrating resin sealer.
Few practitioners tend to coat the wood under natural varnish or lacquer finishes with a thinned combination with the same finish. To create a natural varnish sealer, dilute the varnish 50/50 with turpentine or mineral spirits. To render lacquer sealer, combine equal parts lacquer and lacquer thinner. These sealers can not be used in conjunction with shellac or polyurethane varnish.
Polyurethane varnishes need specific handling. When purchasing, closely read the marks. Certain polyurethanes may be thinned with a special thinner; the maker can prescribe thin varnish coats as sealers with these varnishes. Certain polyurethanes are self-sealing. If stain or filler must be sealed prior to applying polyurethane, ensure that the sealer is consistent with the varnish. Otherwise, a penetrating resin sealer can be used. This absolutely seals the wood, however you may add polyurethane over it for a cleaner finish.
Techniques of Sealing
With a clean blade, apply the sealer accurately and easily around the grain of the wood. Assemble all surfaces equally, paying special care to every end grain. Unsealed end grain absorbs stains and finishes more intensely than the remainder of the wood in a slice.
Allow sufficient time for the sealer to cure completely: approximately two hours for thinned white shellac and approximately one hour for industrial sanding sealer. After that, gently sand the surface with fine-grit sandpaper, rating 7/0. The wood must be very smooth, but not so smooth that it penetrates the sealer. With a tack pad, remove the sanding residue.
If you’re applying a finish directly over sanded wood, it might be appropriate to add several coats of sealer to fully cover the wood’s pores. Allow the first coat of sealer to properly dry before adding a second coat. Sealing extremely porous woods can need many coats.
Staining wooden furniture will significantly improve its appearance and conceal small flaws. Although preparing your piece for staining will require some effort, it will be well worth it until you see the stunning paint.